ANCIENT EARTHWORKS OF OHIO. 235 



accuracy.* The work approaches no where within many feet of 

 the water of the river, but its embankment is in several places 

 carried down into ravines from fifty to one hundred feet deep, 

 and at an angle of thirty degrees crossing a streamlet at the bot- 

 tom, which by showers must often swell to a powerful torrent. 

 But in aU instances the embankment may be ti'aced to within 

 three to eight feet of the stream. Here it appears, that although 

 these little streams have cut their channels through fifty to one 

 hundred feet of thin horizontal layers of blue limestone inter- 

 stratified with indurated clay marl ; not more than three feet of 

 that. excavation has been done since the construction of the earth- 

 works. If the first portion of the denudation was not more rapid 

 than the last, a period of at least thirty to fifty thousand years 

 would be required for the present point of its progress. But the 

 quantity of material removed from such a ravine is as the square 

 of its depth, which would render the last part of the denudation 

 much slower, in vertical descent, than the first part. That our 

 streams have not yet reached a "constant regiiuen," a point be- 

 yond which they cease to act upon their beds, is evident from the 

 vast quantity of solid material transported annually by our rivers, 

 to be added to the great delta of the Mississippi. Finally, I was 

 astonished to see a work simply of earth, after braving the storms 

 of thousands of years, still so entue and well marked. Several 

 circumstances have conhibuted to this. The clay of which it is 

 built is not easily penetrated by water. The bank has been and 

 is still mostly covered by a forest of beech trees, which have 

 woven, a strong web of their roots over their steep sides, and a 

 fine bed of moss (Polytrichum) serves still fmlher to afford pro- 

 tection. Many interesting points of antiquarian research suggest 

 themselves in connection with this examination, but as they have 

 no special geological bearing, I abstain from then* discussion. I 

 will only add, that the full interest of these antiquities will never 

 be developed unless by minute and strictly accurate surveys, call- 

 ing for more labor and expense than are lilvely, under ordinary 

 circumstances, to be bestowed. 



* The " engineers " referred to were, David M. Wilson, John S. Lane, John Silsby, 

 Joseph G. Wilson, James Garrard, Israel L. Garrard, Alfred John, Wm. H. Scott, 

 Andrew McMickin, Thomas F. Jones, and John Locke, Jr. 



